U.S. Pat. No. 6,386,295 and U.S. Pat. No. 6,942,430, which are incorporated here by reference, disclosed the use of vibratory and rotary drivers for the installation of pipe piling. Pipe piles, as used in the installation of structural foundations or geothermal piles, are segments of pipe that must be connected and driven together from the surface to reach the desired depth. Consequently, whether used in connection with vibratory or rotary drivers, the connection between pipe pile segments is vitally important to maximizing the driving power and reducing the possibility of failure of the pipe segment connection points. As the length of the column increases, weaknesses in the junctions between the pipe pile segments weaken the entire column, making it important to limit movement in the junctions.
Thus, prior art methods that require the use of bolts through pipe piles and connectors may lead to high stresses, and hence the risk of mechanical failure, for example, by shearing of the bolt. Where such fasteners are not used, known pipe coupling systems may have other drawbacks. For example, the torque applied to the coupled joint may cause over-threading of the pile and associated coupler, leading to high stresses, improper attachment, and potentially, mechanical failure of the joint.
While it is generally acknowledged that installation of pipe pilings is improved in stability and/or strength when installed with grout or similar material along the exterior of the column, prior art methods, including those disclosing push-out tips, are limited by the actual ability to push out the tip at the bottom of the column, or by difficulty in handling the grout during installation.
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